Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus in which user equipment transmits channel state information in a multi-node system.
Discussion of the Related Art
The data transfer rate over a wireless communication network is recently rapidly increasing. This is because a variety of devices, such as smart phones and tablet PCs which require Machine-to-Machine (M2M) communication and a high data transfer rate, are appearing and spread. In order to meet a higher data transfer rate, carrier aggregation technology and cognitive radio technology for efficiently using more frequency bands and multiple antenna technology and multiple base station cooperation technology for increasing the data capacity within a limited frequency are recently are highlighted.
Furthermore, a wireless communication network is evolving toward a tendency that the density of accessible nodes around a user is increasing. Here, the term ‘node’ may mean antennas or a group of antennas which are spaced apart from one another in a Distributed Antenna System (DAS). However, the node is not limited to the meaning, but may be used as a broader meaning. That is, the node may become a pico eNB (PeNB), a home eNB (HeNB), a Remote Radio Head (RRH), a Remote Radio Unit (RRU), or a relay. A wireless communication system including nodes having a high density may have higher system performance through cooperation between nodes. That is, if the transmission and reception of each node are managed by one control station so that the nodes are operated as antennas or a group of antennas for one cell, the node may have much more excellent system performance as compared with when the nodes do not cooperate with each other and thus each node operated as an independent Base Station (BS) (or an Advanced BS (ABS), a Node-B (NB), an eNode-B (eNB), or an Access Point (AP)). A wireless communication system including a plurality of nodes is hereinafter referred to as a multi-node system.
In a multi-node system, a node which transmits a signal to UE may be different for each UE and a plurality of nodes may be set. Here, each node may send a different reference signal. In this case, UE may measure a channel state between the UE and each node using a plurality of reference signals and periodically feed back the channel state information. In this case, to allocate radio resources through which channel state information will be fed back to UE using what method is problematic.